The Research Of Two-band White Organic Light Emitting Diodes

Since the early1990s, professor Kido published an article about white organic light emitting diodes on science. After20years of development, the white organic light emitting diodes have made great progress. The white organic light emitting diodes as a strong contender for the next generation lighting technology due to their low heat,low power consumption,flexible and can produce high-quality white light and so on.However,to further improve the efficiency and reduce production costs is still an important factor that affecting the massive popularity. In this study, based on the above issues and the present situation of the white organic light emitting diodes, two-band white organic light emitting diodes were designed and preparation, and to improve the WOLEDs performance through a variety of ways. The study mainly includes five parts as follows:Firstly, this part summarizes the characteristics, development history and present situation of OLED. Then outlines the OLED’s structure and emitting principle, it can be summarized as the carrier injection, carrier transport, carrier recombination and electroluminescent. And summarizes the different approaches to realize WOLEDs.Secondly, the specific preparation process of OLED is described. It includes substrate etching process, substrate surface cleaning process and the film preparation process. And outlines the OLED performance parameters, including the current-voltage-luminance relationship, chromaticity coordinates, color temperature and color rendering index, efficiency, etc.. It also describes the organic material, including the hole injecting and transporting material, the host material, the light emitting material and the electron transport material.Thirdly, a device based on the blue phosphorescent material and a red fluorescent material was prepared. Then through adoption and adding the interlayers to regulate the color of the light. Ultimately, the white organic light emitting diodes were prepared. Fourthly, this part of the study is based on the NPB as a hole transport material and blue fluorescent material to design device. DCJTB is the red fluorescent material in the device. By changing the device structure step by step, the white organic light emitting diodes were prepared.Finally, Phosphorescent white organic light-emitting diodes with double light-emitting layers were fabricated, which were based on phosphorescent blue emitter (FIrpic) and red emitter (Ir(MDQ)2acac). A hole transporting wide-band-gap materials were introduced between the emitting layers as an interlayer. The results show that the interlayer can play an important role of balancing charge carriers, and blocking energy transfer between the emitting layers. When an appropriate thickness of the interlayer were selected, the device performances were found to be significantly enhanced, with maximum current efficiency from3.4cd/A to13.2cd/A.